Conventionally, power transmission apparatus of various mechanisms for transmitting power of the input shaft to an output shaft have been provided, in which an apparatus using planetary cones as shown in FIG. 2 is provided.
The prior art power transmission apparatus shown in FIG. 2 will simply be described. An input disc 102 is integral with an axial end of an input shaft 101, a cam disc 105 is provided at an output shaft 103 through a pressure governor cam 104, between the input disc 102 and the cam disc 105 are interposed a plurality of planetary cones 107 rotatably supported on a retainer 106, and a ring-like speed control member 108 is brought into frictional contact with a conical portion of each planetary cone 107, so that the speed control member 108 is adjusted in position in the direction of the arrow E or F, thereby transmitting power from the input shaft 101 to the output shaft 103 at a predetermined reduction ratio.
In detail, when the input shaft 101 is rotatably driven to drive the input disc 102, the planetary cones 107 in contact with the outer periphery of the input disc 102, and the retainer 106 rotates depending on the contact position of the speed control member 108 with the cones 107, so that the planetary cones 107 revolve. Thus, the rotation and revolution of each planetary cone 107 allow the cam disc 105 to rotate at a predetermined reduction ratio with respect to the input shaft 101.
In addition, in FIG. 2, the speed control member 108 is displaced in the direction of the arrow E so as to reduce the speed, and in the direction of the arrow F so as to increase the speed, the speed control member 108 being positioned at the crest of each conical portion 107a, whereby the cam disc 105 rotates in an equal number of rotations to the input shaft 101.
The conventional power transmission apparatus constructed as above-mentioned transmits power from the input shaft 101 only to the output shaft 103. Therefore, the power can be taken out in only one system from the output shaft 103, but not in two systems.
Accordingly, in a case where the above-mentioned power transmission apparatus is used in, for example, a slurry agitator, i.e. when agitating vanes disposed in an agitating tank are coupled with the output shaft 103 so as to agitate slurry in the agitating tank by the vanes, the vanes are only driven by power in one system taken out from the input shaft 101 to the output shaft 103, whereby the slurry to be agitated, even when moved at the central portion of the tank, is less moved between the central portion and the peripheral portion of the same. As the result, the entire shearing effect on the slurry by the vanes is not obtainable, thereby causing the defect of deteriorating the agitation efficiency.
In order to improve the entire shearing effect with respect to the slurry, it is considered that two drive sources be used to drive agitating vanes at a peripheral portion and a central portion of the tank in a different number of rotations and in different directions. Such means, however, requires an additional drive source, thereby creating the problem in that the agitator becomes not only complicated in construction but also large-sized as a whole.